The present invention refers in general to cutting and drilling machines for opening holes, preferably in composite structures within the aeronautical manufacturing field.
An object of the invention, is to provide a drilling machine capable of opening automatically and in one-shot (simultaneously), two or more holes in a structure with a crosspiece configuration.
Another object of the invention is to reduce drilling cycle time, reduce drilling defects, and to improve ergonomic of the machine.
One known type of drilling machines are the so-called Automatic Drilling Units (ADU), that are based on a pneumatic drill device that operates one or more drilling tools with constant drilling parameters during the whole process. ADU's allow accurate control of drilling parameters to obtain high-quality drills.
However, due to the size of conventional ADU's, these normally cannot be used for drilling in areas of difficult access, like in the inner surfaces of a crosspiece, for example for opening holes for receiving the so-called “chicken-rivets.”
“Chicken-rivets” are used, even if they are not actually necessary, to assure a sturdy bond between two composite pieces, but they are used nevertheless to prevent spontaneous, and unpredictable failure of bonds in general, like peeling of fiber-reinforced plastics materials.
Therefore, in these areas of difficult access, drilling operations are usually performed manually with a machine having only one spindle, with which an operator opens holes one by one.
Obviously, this manual process is very slow, and the quality of the drill depends on the operator ability, so that parameters like advance speed and axial force depends on the skills of the human operator. Consequently, due to human imperfection and the difficulty of the area to be drilled, the proliferation of defects is common with the consequent non-quality costs.
There is the need, especially in the aeronautical industry, to improve drilling operations in terms of quality and yield times, so as to reduce production cost due to drilling operations.